A conventional bipolar transistor includes device isolation regions formed on a semiconductor substrate at a predetermined depth using high impurity concentration of a conductive type identical with that of the semiconductor substrate. The conventional bipolar transistor also includes a buried layer formed between the device isolation regions at a depth deeper than that of the device isolation regions and having a conductive type opposite to that of the semiconductor substrate. Additionally, such devices typically include an epitaxial layer formed on the buried layer and having the conductive type opposite to that of the semiconductor substrate.
The conventional transistor includes a base region formed in the device region in predetermined depth and size, an emitter region formed within the base region at a predetermined depth, and a collector region formed within the epitaxial layer in predetermined depth and size at a predetermined distance from the base region.
Also, the conventional bipolar transistor includes an upper dielectric layer formed over the device isolation region, the device region, the base region, and the emitter and collector regions, and having contact holes for connecting the base, emitter, and collector regions to outside, and a metal wiring layer formed from upper surfaces of the regions to the dielectric layer through the contact hole.
The height difference between the epitaxial layer and the semiconductor substrate of the bipolar transistor is typically used as an arrangement key for subsequent processing after the epitaxial layer is formed.
However, in case of using P+ type semiconductor substrate, a P+ type epitaxial layer rises above the N+ type buried layer being slanted at a 45 degree angle such that the position of the arrangement key becomes inconsistent with the buried layer.